scholarly journals Octopamine promotes rhythmicity but not synchrony in a bilateral pair of bursting motor neurons in the feeding circuit of Aplysia

2010 ◽  
Vol 213 (7) ◽  
pp. 1182-1194 ◽  
Author(s):  
C. Martinez-Rubio ◽  
G. E. Serrano ◽  
M. W. Miller
Keyword(s):  
Motor Neurons ◽  
Bilateral Pair

Endogenous Motor Neuron Properties Contribute to a Program-Specific Phase of Activity in the Multifunctional Feeding Central Pattern Generator of Aplysia

2007 ◽  
Vol 98 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Geidy E. Serrano ◽  
Clarissa Martínez-Rubio ◽  
Mark W. Miller
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
Central Pattern Generators ◽  
Ingestive Behavior ◽  
Membrane Properties ◽  
Motor Patterns ◽  
Effector System ◽  
Bilateral Pair ◽  
Pattern Generators ◽  
Specific Phase

Multifunctional central pattern generators (CPGs) are circuits of neurons that can generate manifold actions from a single effector system. This study examined a bilateral pair of pharyngeal motor neurons, designated B67, that participate in the multifunctional feeding network of Aplysia californica. Fictive buccal motor programs (BMPs) were elicited with four distinct stimulus paradigms to assess the activity of B67 during ingestive versus egestive patterns. In both classes of programs, B67 fired during the phase of radula protraction and received a potent inhibitory postsynaptic potential (IPSP) during fictive radula retraction. When programs were ingestive, the retraction phase IPSP exhibited a depolarizing sag and was followed by a postinhibitory rebound (PIR) that could generate a postretraction phase of impulse activity. When programs were egestive, the depolarizing sag potential and PIR were both diminished or were not present. Examination of the membrane properties of B67 disclosed a cesium-sensitive depolarizing sag, a corresponding Ih-like current, and PIR in its responses to hyperpolarizing pulses. Direct IPSPs originating from the influential CPG retraction phase interneuron B64 were also found to activate the sag potential and PIR of B67. Dopamine, a modulator that can promote ingestive behavior in this system, enhanced the sag potential, Ih-like current, and PIR of B67. Finally, a pharyngeal muscle contraction followed the radula retraction phase of ingestive, but not egestive motor patterns. It is proposed that regulation of the intrinsic properties of this motor neuron can contribute to generating a program-specific phase of motor activity.

Segmental giant: evidence for a driver neuron interposed between command and motor neurons in the crayfish escape system

1982 ◽  
Vol 47 (5) ◽  
pp. 761-781 ◽  
Author(s):  
A. Roberts ◽  
F. B. Krasne ◽  
G. Hagiwara ◽  
J. J. Wine ◽  
A. P. Kramer
Keyword(s):  
Motor Neuron ◽  
Motor Neurons ◽  
High Frequency ◽  
Functional Significance ◽  
Escape Behavior ◽  
Dendritic Branch ◽  
Command Neurons ◽  
Firing Threshold ◽  
Conventional Tests ◽  
Bilateral Pair

1. The giant command neurons for tailflip escape behavior in crayfish have been thought to excite the nongiant fast flexor (tailflip producing) motor neurons (FFs) via monosynaptic connections. We show here that excitation of FFs instead occurs via a bilateral pair of segmental giant neurons (SGs) interposed between the command axons and FFs in each segment. 2. Anatomically, the SGs appear to make numerous contacts with ipsilateral command axons and FFs and fewer contacts contralaterally. In contrast, the command axons have only sparse direct connections to the FFs. An SG has an axon in the ipsilateral first ganglionic root and may be a modified swimmeret motor neuron. 3. Each SG is depolarized well beyond threshold by the firing of an ipsilateral command axon and is depolarized to near threshold by the firing of a contralateral command axon. The synapses between command axons and SGs are electrical and probably rectifying. 4. Each FF is excited to a level near firing threshold by the SG ipsilateral to its axon and is excited weakly by the contralateral SG. The synapses between SGs and FFs are electrical and nonrectifying. 5. Variations in excitatory postsynaptic potentials (EPSPs) recorded in FFs during prolonged, high-frequency firing of the command axons can be accounted for by refractoriness of SG spikes, as opposed to refractoriness of dendritic branch spikes as had previously been delivered. 6. These findings illustrate the limitations of conventional tests for monosynapticity. 7. The functional significance of having driver neurons interposed between command neurons and motor neurons is discussed.

Conditional Rhythmicity and Synchrony in a Bilateral Pair of Bursting Motor Neurons in Aplysia

2006 ◽  
Vol 96 (4) ◽  
pp. 2056-2071 ◽  
Author(s):  
Geidy E. Serrano ◽  
Mark W. Miller
Keyword(s):  
Motor Neurons ◽  
Aplysia Californica ◽  
Burst Activity ◽  
Feeding System ◽  
Postsynaptic Potentials ◽  
Potential Source ◽  
Bath Application ◽  
Bilateral Pair ◽  
Driver Potential ◽  
Rhythmic Burst

This investigation examined the activity of a bilateral pair of motor neurons (B67) in the feeding system of Aplysia californica. In isolated ganglia, B67 firing exhibited a highly stereotyped bursting pattern that could be attributed to an underlying TTX-resistant driver potential (DP). Under control conditions, this bursting in the two B67 neurons was infrequent, irregular, and asynchronous. However, bath application of the neuromodulator dopamine (DA) increased the duration, frequency, rhythmicity, and synchrony of B67 bursts. In the absence of DA, depolarization of B67 with injected current produced rhythmic bursting. Such depolarization-induced rhythmic burst activity in one B67, however, did not entrain its contralateral counterpart. Moreover, when both B67s were depolarized to potentials that produced rhythmic bursting, their synchrony was significantly lower than that produced by DA. In TTX, dopamine increased the DP duration, enhanced the amplitude of slow signaling between the two B67s, and increased DP synchrony. A potential source of dopaminergic signaling to B67 was identified as B65, an influential interneuron with bilateral buccal projections. Firing B65 produced bursts in the ipsilateral and contralateral B67s. Under conditions that attenuated polysynaptic activity, firing B65 evoked rapid excitatory postsynaptic potentials in B67 that were blocked by sulpiride, an antagonist of synaptic DA receptors in this system. Finally, firing a single B65 was capable of producing a prolonged period of rhythmic synchronous bursting of the paired B67s. It is proposed that modulatory dopaminergic signaling originating from B65 during consummatory behaviors can promote rhythmicity and bilateral synchrony in the paired B67 motor neurons.

Androgen-induced plasticity at a “vocal” neuromuscular synapse

1994 ◽  
Vol 52 ◽  
pp. 32-33
Author(s):  
Darcy B. Kelley ◽  
Martha L. Tobias ◽  
Mark Ellisman
Keyword(s):  
Xenopus Laevis ◽  
Motor Neurons ◽  
Sexual Differentiation ◽  
Molecular Basis ◽  
Neuromuscular Synapse ◽  
Sexually Dimorphic ◽  
Intracellular Protein ◽  
Developmental Program ◽  
Androgen Action ◽  
Clawed Frog

Brain and muscle are sexually differentiated tissues in which masculinization is controlled by the secretion of androgens from the testes. Sensitivity to androgen is conferred by the expression of an intracellular protein, the androgen receptor. A central problem of sexual differentiation is thus to understand the cellular and molecular basis of androgen action. We do not understand how hormone occupancy of a receptor translates into an alteration in the developmental program of the target cell. Our studies on sexual differentiation of brain and muscle in Xenopus laevis are designed to explore the molecular basis of androgen induced sexual differentiation by examining how this hormone controls the masculinization of brain and muscle targets.Our approach to this problem has focused on a highly androgen sensitive, sexually dimorphic neuromuscular system: laryngeal muscles and motor neurons of the clawed frog, Xenopus laevis. We have been studying sex differences at a synapse, the laryngeal neuromuscular junction, which mediates sexually dimorphic vocal behavior in Xenopus laevis frogs.

Effects of HBO with reduction of iNOS and HIF -1α in motor neurons after transient spinal cord ischemia in rabbits

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S452-S452
Author(s):  
Noritaka Murakami ◽  
Masahiro Sakurai ◽  
Takashi Horinouchi ◽  
Jun Ito ◽  
Shin Kurosawa ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Motor Neurons ◽  
Spinal Cord Ischemia

Co-Culture of ES Cell-Derived Motor Neurons and Myotubes Show the Formation of Neuromuscular Junctions and Changes in Gene Expression

2006 ◽  
Vol 22 (06) ◽  
Author(s):  
Aleid Ruijs ◽  
Tateki Kubo ◽  
Jae Song ◽  
Milan Ranka ◽  
Mark Randolph ◽  
...  
Keyword(s):  
Gene Expression ◽  
Motor Neurons ◽  
Neuromuscular Junctions ◽  
Es Cell
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